JP2019084980A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire that is able to achieve both hindering of deterioration of rolling resistance and reduction of road noise while improving wet steering stability.SOLUTION: A pneumatic tire, which is mounted on a vehicle so as to rotate in a specified rotational direction, comprises: a shoulder land part 23 located in a tire width direction outside each of outermost main grooves 35 located both ends in the tire width direction; a shoulder groove part 40 formed in the shoulder land part 23 and apart from the corresponding outermost main groove 35; and a plane part 70, which is an area disposed between the corresponding outermost main groove 35 and the corresponding shoulder groove part 40 and having no grooves over the entire circumference in a tire circumferential direction. At least part of the plane part 70 is located in the range of 22% or more but 38% or less of a ground width TW in the tire width direction from a tire equator surface CL. In the plane part 70, the total width in the tire width direction is in the range of 17% or more but 30% or less of the ground width TW. In a tread surface 10, a groove area ratio of grooves, other than the plurality of main grooves 30, is in the range of 2% or more but 8% or less.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire.

  In pneumatic tires, a plurality of grooves are formed on the tread surface for the purpose of draining water between the tread surface and the road surface when traveling on a wet road surface, but the grooves on the tread surface have steering stability and resistance It greatly affects the performance other than drainage, such as wear resistance and ride comfort. Therefore, in the conventional pneumatic tire, for example, as in Patent Documents 1 to 3, the balance of the performance required for the pneumatic tire is achieved by devising the groove position, the groove shape, the groove width, etc. There is.

JP, 2017-47853, A JP, 2014-184828, A JP, 2015-131603, A

  Here, in recent years, in order to improve the fuel consumption at the time of vehicle traveling, there is an increasing demand for reducing the rolling resistance at the time of rolling of the pneumatic tire. One way to reduce the rolling resistance is to reduce the rubber volume of the tread portion. However, when the rubber volume of the tread portion is reduced, the rigidity of the tread portion is reduced, so that the tread portion is easily bent, and road noise which is noise generated due to the unevenness of the road surface may be increased. Specifically, among road noises, it is known that the medium frequency band of 250 Hz to 315 Hz is affected by the vibration of the tread portion or the like when the pneumatic tire rolls, and the medium frequency road noise is a tread portion etc. The influence of the cross-section second-order eigenfrequency at the time of vibration is large. For this reason, when the rubber volume of the tread portion is reduced paying attention only to the reduction of the rolling resistance, there is a possibility that the cross-sectional second-order natural frequency becomes low due to the reduction of the rubber volume, and the road noise becomes large.

  On the other hand, reducing this road noise is also one of the important performances required of pneumatic tires. As a method for reducing the road noise, for example, adjusting the vibration state of the tread portion by adjusting the structural aspect such as adjusting the belt stiffness may be mentioned. However, when the adjustment of the structural surface is performed to reduce the road noise, the rolling resistance may be increased due to the change in rigidity.

  In addition, when the structural surface of the pneumatic tire is adjusted, the effect of the adjustment affects the various performances of the pneumatic tire, so when adjusting the structural surface to reduce road noise, the tread surface There is also a possibility that the wet steering stability, which is the steering stability on a wet road surface, which is a performance required for the formed groove, may be affected. For example, when improving the wet steering safety by devising the form of the groove, when the structure surface is adjusted to reduce road noise, the grounding shape on the road surface is suitable for improving the wet steering safety. There is a risk that it will not be possible to obtain the desired wet steering stability. As described above, it has been very difficult to reduce road noise while securing other performances such as rolling resistance and wet handling.

  The present invention has been made in view of the above, and it is an object of the present invention to provide a pneumatic tire capable of achieving both suppression of deterioration of rolling resistance and reduction of road noise while improving wet handling. To aim.

  In order to solve the problems described above and to achieve the object, a pneumatic tire according to the present invention is an air mounted on the vehicle so as to rotate in a designated rotation direction about a rotation axis when the vehicle advances. A tire including a plurality of main grooves formed on a tread surface and extending in the circumferential direction of the tire, a plurality of land portions defined by the main grooves, and both ends of the plurality of main grooves in the tire width direction. A shoulder land portion, which is the land portion located on the outer side in the tire width direction, of the outermost main groove located on the ground width end and disposed on the inner side in the tire width direction, and the shoulder land portion The groove is disposed between the shoulder groove portion separated from the outer main groove, the outermost main groove on both sides of the tire center line in the tire width direction, and the shoulder groove portion, and the groove extends over the entire circumferential direction of the tire. Is not formed A plane portion which is a region, at least a portion of which is located within a range of 22% to 38% of the ground contact width in the tire width direction from the tire width direction center line; The total width of the plurality of plain portions in the tire width direction is in the range of 17% to 30% of the ground contact width, and the tread surface is a groove area of the groove excluding the plurality of main grooves The ratio is in the range of 2% to 8%.

  Further, in the pneumatic tire, it is preferable that a width of the plain portion in a tire width direction is in a range of 8.5% to 15% of the contact width.

  In the pneumatic tire, the outermost main groove has a distance from the center line in the tire width direction to the groove width center of the outermost main groove in a range of 10% to 20% of the contact width. It is preferable that the plurality of main grooves are disposed at positions, and the width of each of the plurality of main grooves is in the range of 3% to 10% of the contact width.

  In the pneumatic tire, the number of main grooves formed in the tread surface is two, and the width of each of the two main grooves is in the range of 5% to 10% of the contact width. Is preferred.

  In the pneumatic tire, the number of main grooves formed in the tread surface is three, and the width of each of the three main grooves is in the range of 3% to 7% of the contact width. Is preferred.

  In the pneumatic tire, a plain portion inner groove portion extending in the tire width direction and having an inner end in the tire width direction communicating with the outermost main groove is provided between the plain portion and the outermost main groove. Preferably, the plain portion is provided on the outer side in the tire width direction from the position in the tire width direction of the outer end of the plain portion inner groove portion in the tire width direction.

  In the pneumatic tire, it is preferable that a sipe extending in the tire width direction and in communication with the main groove is formed in the land portion disposed between the main grooves.

  In the pneumatic tire, a sipe extending in the tire width direction and between at least one end in the tire width direction communicates with the main groove between the plain portion and the main groove and between the main grooves. A plurality of the sipes are disposed in the tire circumferential direction, and the plurality of sipes extend in the tire width direction and incline in the tire circumferential direction with respect to the tire width direction, and the tire width When going from the direction center line side to the tire width direction outer side, all the directions in the tire circumferential direction are inclined in the same direction, and a plurality of the sipes are adjacent to the land portions adjacent to each other via the outermost main groove. It is preferable that the sipes formed and in communication with the same outermost main groove be disposed at positions extending along each other.

  In the pneumatic tire, the shoulder groove portion is disposed between a plurality of shoulder lug grooves extending in the tire width direction and the shoulder lug grooves adjacent in the tire circumferential direction and extends in the tire width direction. It is preferable to have and.

  Further, in the pneumatic tire, it is preferable that a recess be formed on the shoulder land portion at the tire width direction outer side of the ground contact end.

  In the pneumatic tire, it is preferable that a groove area ratio of the main groove in the tread surface be in a range of 15% to 20%.

  ADVANTAGE OF THE INVENTION The pneumatic tire which concerns on this invention has an effect that suppression of the deterioration of rolling resistance and reduction of road noise can be made compatible, improving wet handling property.

FIG. 1 is a meridional sectional view showing the main parts of the pneumatic tire according to the first embodiment. FIG. 2 is a plan view of the tread portion of the pneumatic tire shown in FIG. FIG. 3 is a detailed view of part A of FIG. FIG. 4 is an explanatory view of the positional relationship between the inter-main groove sipe shown in FIG. 3 and the plane portion inner sipe. FIG. 5 is an explanatory view of the widths and positions of the main groove and the plane portion shown in FIG. FIG. 6 is an explanatory view showing the relationship between the tread pattern shown in FIG. 2 and the magnitude of the amplitude in the cross-section second-order natural vibration mode. FIG. 7 is a plan view of a tread portion of a pneumatic tire according to a second embodiment. FIG. 8A is a chart showing the results of performance tests of pneumatic tires. FIG. 8B is a chart showing the results of performance tests of pneumatic tires. FIG. 8C is a chart showing the results of performance tests of pneumatic tires.

  Below, an embodiment of a pneumatic tire concerning the present invention is described in detail based on a drawing. The present invention is not limited by this embodiment. Further, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art and those that are substantially the same.

Embodiment 1
In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, the tire radial inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial outer side Means the side away from the rotation axis in the tire radial direction. Further, the tire circumferential direction refers to a circumferential direction with the rotation axis as a central axis. The tire width direction means a direction parallel to the rotation axis, the tire width direction inner side in the tire width direction toward the tire equatorial plane (tire equator line) CL, and the tire width direction outer side in the tire width direction It says the side away from tire equatorial plane CL. The tire equatorial plane CL is a plane perpendicular to the rotation axis of the pneumatic tire 1 and passing through the center of the tire width of the pneumatic tire 1, and the tire equatorial plane CL is the center of the pneumatic tire 1 in the tire width direction. The position in the tire width direction coincides with the center line in the tire width direction which is the position. The tire width is the width in the tire width direction of the portions positioned outermost in the tire width direction, that is, the distance between the portions most distant from the tire equatorial plane CL in the tire width direction. The tire equator line is a line which is on the tire equator plane CL and extends along the circumferential direction of the pneumatic tire 1.

  FIG. 1 is a meridional sectional view showing the main part of the pneumatic tire 1 according to the first embodiment. Here, the pneumatic tire 1 shown in FIG. 1 is the pneumatic tire 1 in which the rotational direction at the time of wearing the vehicle is designated, that is, the rotational direction designated about the rotational axis at the time of forward movement of the vehicle. The pneumatic tire 1 is mounted on a vehicle so as to rotate. The pneumatic tire 1 also has a rotation direction indicator (not shown) that indicates the rotation direction. The rotation direction display unit is configured by, for example, a mark or unevenness provided on the sidewall portion 4 of the tire. Moreover, the pneumatic tire 1 according to the present embodiment is a pneumatic tire 1 mainly used for a passenger car. In the following description, the first arrival side in the tire rotation direction is the rotation direction side when the pneumatic tire 1 is rotated in the designated direction, and the pneumatic tire 1 is mounted on a vehicle and rotated in the designated direction to travel In this case, it is the side that contacts the road surface first or leaves the road surface first. Further, the rear attachment side in the tire rotational direction is the opposite side of the rotational direction when the pneumatic tire 1 is rotated in the designated direction, and the pneumatic tire 1 is mounted on a vehicle and rotated in the designated direction to travel In this case, it is a side where it comes in contact with the road surface after the part located on the first arrival side, or leaves the road surface after the part located on the first arrival side.

  The pneumatic tire 1 according to the present embodiment includes a tread portion 2, shoulder portions 3 on both sides of the tread portion 2, and sidewall portions 4 and bead portions 5 which are sequentially connected from the shoulder portions 3. The pneumatic tire 1 further includes a carcass layer 6, a belt layer 7, and a belt reinforcing layer 8.

  The tread portion 2 is made of a rubber material (tread rubber), and is exposed at the outermost side in the tire radial direction of the pneumatic tire 1, and the outer peripheral surface thereof becomes the contour of the pneumatic tire 1. The outer peripheral surface of the tread portion 2 is configured as a tread surface 10 which is a surface that can contact the road surface mainly during traveling.

  The shoulder portions 3 are portions of the tread portion 2 on both outer sides in the tire width direction. Further, the sidewall portion 4 forms a portion of the pneumatic tire 1 that is exposed to the outermost side in the tire width direction. Further, the bead portion 5 has a bead core 15 and a bead filler 16. The bead core 15 is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead filler 16 is a rubber material disposed in a space formed by the end in the tire width direction of the carcass layer 6 being folded back at the position of the bead core 15.

  The carcass layer 6 has its tire width direction end portions folded back from the inside in the tire width direction to the outside in the tire width direction by a pair of bead cores 15 and wound in a toroidal shape in the tire circumferential direction to form a tire skeleton. It is a thing. The carcass layer 6 is obtained by coating a plurality of carcass cords (not shown) arranged side by side at an angle in the tire circumferential direction while the angle with respect to the tire circumferential direction is along the tire meridian direction, with a coat rubber. The carcass cord is made of, for example, an organic fiber such as polyester, rayon or nylon. The carcass layer 6 is provided in at least one layer.

  The belt layer 7 has a multi-layered structure in which at least two layers of belts 7a and 7b are stacked, and is disposed on the tread radial direction outer side of the carcass layer 6 in the tread portion 2 and covers the carcass layer 6 in the tire circumferential direction It is. The belts 7a and 7b are obtained by coating a plurality of cords (not shown) arranged in parallel at a predetermined angle (for example, 20 ° to 30 °) with the circumferential direction of the tire with a coated rubber. The cord is made of, for example, steel or an organic fiber such as polyester, rayon or nylon. The overlapping belts 7a and 7b are arranged such that their cords cross each other.

  The belt reinforcing layer 8 is disposed on the outer side in the tire radial direction, which is the outer periphery of the belt layer 7, and covers the belt layer 7 in the tire circumferential direction. The belt reinforcing layer 8 is one in which a plurality of cords (not shown) substantially parallel to the tire circumferential direction and arranged in parallel in the tire width direction are coated with a coat rubber. The cord is made of, for example, steel or an organic fiber such as polyester, rayon or nylon, and the angle of the cord is within ± 5 ° with respect to the tire circumferential direction. The belt reinforcing layer 8 shown in FIG. 1 is disposed so as to cover the end of the belt layer 7 in the tire width direction. The configuration of the belt reinforcing layer 8 is not limited to the above and is not clearly shown in the drawings, but is configured to cover the entire belt layer 7 or has, for example, two reinforcing layers, The reinforcing layer is formed to be larger in the tire width direction than the belt layer 7 and arranged to cover the entire belt layer 7, and the reinforcing layer on the outer side in the tire radial direction is arranged to cover only the tire width direction end of the belt layer 7 Alternatively, for example, two reinforcing layers may be provided, and each reinforcing layer may be disposed so as to cover only the end portion of the belt layer 7 in the tire width direction. That is, the belt reinforcing layer 8 overlaps at least the tire width direction end of the belt layer 7. Further, the belt reinforcing layer 8 is provided by winding a strip material having a width of, for example, about 10 mm in the tire circumferential direction.

  FIG. 2 is a plan view of the tread portion 2 of the pneumatic tire 1 shown in FIG. A plurality of main grooves 30 extending in the tire circumferential direction are formed in the tread surface 10 of the tread portion 2, and in the first embodiment, three main grooves 30 are formed. The three main grooves 30 have a center main groove 31 disposed on the tire equatorial plane CL, and two outermost main grooves 35 positioned at both ends of the three main grooves 30 in the tire width direction. ing. The two outermost main grooves 35 are both disposed on the inner side in the tire width direction of the ground contact end T, and the center main groove 31 is disposed between the two outermost main grooves 35. In this case, the ground contact end T is formed by rimming the pneumatic tire 1 on a regular rim and filling with a regular internal pressure, and the load is equivalent to 88% of the regular load, placed perpendicular to the flat plate in a stationary state. And the outermost ends in the tire width direction of the region in contact with the flat plate in the tread surface 10, and is continuous in the tire circumferential direction.

  Here, the normal rim is a “standard rim” defined by JATMA, a “design rim” defined by TRA, or a “measuring rim” defined by ETRTO. The normal internal pressure is the "maximum air pressure" defined by JATMA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFlation PRESSURES" defined by TRA, or "INFLATION PRESSURES" defined by ETRTO. The normal load is the maximum value of "maximum load capacity" defined by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or "LOAD CAPACITY" defined by ETRTO.

  Further, the main groove 30 refers to a vertical groove at least a part of which extends in the tire circumferential direction. Generally, the main groove 30 has a groove width of 5 mm or more, a groove depth of 7.5 mm or more, and internally has a tread wear indicator (slip sign) indicating the end of wear. In the first embodiment, the main groove 30 has a groove width of 5 mm or more, a groove depth of 5 mm or more, and the tire equator line (center line intersects the tire equatorial plane CL and the tread surface 10 Substantially parallel to The main groove 30 may extend linearly in the tire circumferential direction, or may be provided in a wave shape or zigzag.

  Further, a plurality of land portions 20 defined by the main groove 30 are formed on the tread surface 10. As land part 20, center land part 21 which is land part 20 located between adjacent center main groove 31 and outermost main groove 35, and land part located in the tire width direction outside of outermost main groove 35 A shoulder land 23 which is 20 is provided. In other words, both ends in the tire width direction of the center land portion 21 are defined by the center main groove 31 and the outermost main groove 35, and the shoulder land portion 23 has the inner end in the tire width direction as the outermost main It is defined by the groove 35. All of the land portions 20 are formed as rib-like land portions 20 extending in the tire circumferential direction.

  Among the plurality of land portions 20 defined by the main groove 30 as described above, the shoulder land portion 23 is formed with a shoulder groove portion 40 which is a groove formed to be separated from the outermost main groove 35 . The shoulder groove portion 40 has a plurality of shoulder lug grooves 46 extending in the tire width direction and shoulder sipe 47 which is a sipe disposed between the shoulder lug grooves 46 adjacent in the tire circumferential direction and extending in the tire width direction. doing. That is, in the shoulder lug grooves 46 and the shoulder sipes 47, the plurality of shoulder lug grooves 46 and the shoulder sipes 47 are alternately disposed in the tire circumferential direction.

  The sipe referred to here is a groove formed in a narrow groove shape on the tread surface 10, and the pneumatic tire 1 is rim-assembled on a normal rim, and the narrow groove is formed under no load condition under normal internal pressure conditions. When the narrow groove is positioned on the portion of the ground contact surface formed on the flat plate when the wall surfaces are not in contact with each other but are loaded in the vertical direction on the flat plate, or when the land portion 20 in which the narrow groove is formed falls. The wall surfaces constituting the narrow groove, or at least a part of the portion provided on the wall surfaces are in contact with each other due to the deformation of the land portion 20.

  The shoulder lug grooves 46 and the shoulder sipes 47 are both curved in the tire circumferential direction with respect to the tire width direction while extending in the tire width direction. The shoulder lug grooves 46 and the shoulder sipes 47 are both curved in the direction in which the inclination angle with respect to the tire width direction decreases as going from the inside to the outside in the tire width direction. Further, the shoulder lug grooves 46 and the shoulder sipes 47 respectively formed on the shoulder land portions 23 provided at two locations on both sides in the tire width direction have a direction toward the tire circumferential direction when going from the inside to the outside in the tire width direction. , All in the same direction. That is, the shoulder lug grooves 46 and the shoulder sipes 47 are all inclined toward the same direction in the tire circumferential direction as they go from the inside to the outside in the tire width direction. In the first embodiment, the shoulder lug grooves 46 and the shoulder sipes 47 are inclined in the direction from the front to the rear in the tire rotation direction from the inside to the outside in the tire width direction.

  Further, in the shoulder lug groove 46, the inner end 46a of the shoulder lug groove 46 in the tire width direction terminates in the shoulder land portion 23, and the outer end 46b in the tire width direction is the tire width direction outer end of the tread surface 10. It is open at the design end E. Here, the design end E is the tire width direction outer side of the ground contact end T, and refers to the tire width direction outermost end of the tread portion 2, and is the tire width direction outermost end where grooves are formed in the tread portion 2. In FIG. 2, the design end E is continuously shown in the tire circumferential direction. That is, on the dry and flat road surface, the tread portion 2 is a region on the design end E side of the ground contact end T, which is a region not normally in contact with the road surface.

  On the other hand, in the shoulder sipe 47, both the inner end 47a and the outer end 47b in the tire width direction end in the shoulder land portion 23. Further, the shoulder lug groove 46 and the shoulder sipe 47 have a position in the tire width direction of the inner end 46 a in the tire width direction of the shoulder lug groove 46 and a tire width direction of the inner end 47 a in the tire width direction of the shoulder sipe 47 And the position at the same position.

  The shoulder lug groove 46 thus formed has a groove width in the range of 1.5 mm to 6 mm and a groove depth in the range of 2 mm to 8 mm. The shoulder sipe 47 has a groove depth of 2 mm or more and 8 mm or less within a range of 0.1 mm or more and 2 mm or less.

  FIG. 3 is a detailed view of part A of FIG. In the vicinity of the outermost main groove 35 in the shoulder land portion 23, a plane portion inner groove portion 50 which defines a plane portion 70 described later is formed. In the first embodiment, the plane portion inner groove portion 50 is formed by the plane portion inner sipe 51 formed as a sipe. The plain inner side sipe 51 is inclined in the tire circumferential direction with respect to the tire width direction while extending in the tire width direction, and the inclination direction in the tire circumferential direction is the same shoulder land portion 23 as the respective plain inner side sipes 51. It is in the same direction as the inclined direction of the shoulder lug groove 46 and the shoulder sipe 47 formed in the. That is, in the plain portion inner sipes 51 formed in the shoulder land portions 23 on both sides in the tire width direction, the inclination directions in the tire circumferential direction with respect to the tire width direction are opposite to each other. In the first embodiment, like the shoulder lug grooves 46 and the shoulder sipe 47, the plain portion inner sipe 51 moves from the front to the rear in the tire rotation direction from the inner side to the outer side in the tire width direction. It is inclined.

  Further, in the plain portion inner sipe 51, the inner end 51a in the tire circumferential direction communicates with the outermost main groove 35, and the outer end 51b in the tire circumferential direction terminates in the shoulder land portion 23. The outer end 51 b of the plain portion inner sipe 51 is located on the inner side in the tire width direction relative to the positions of the inner end 46 a of the shoulder lug groove 46 and the inner end 47 a of the shoulder sipe 47 in the tire width direction.

  As described above, the inner end 46a of the shoulder lug groove 46 and the inner end 47a of the shoulder sipe 47 and the outer end 51b of the plain inner side sipe 51 are separated in the tire width direction, and the shoulder lug groove Since the 46 and the shoulder sipes 47 and the plain portion inner sipes 51 do not overlap in the tire circumferential direction, the shoulder land portion 23 is a plain portion in which no groove is formed over the entire circumferential direction of the tire. 70 are provided. The plain portions 70 are respectively provided on the shoulder land portions 23 on both sides in the tire width direction, that is, they are respectively disposed between the outermost main grooves 35 and the shoulder groove portions 40 on both sides of the tire equatorial plane CL in the tire width direction. It is set up.

  More specifically, the plain portion 70 extends from the position in the tire width direction of the outer end portion 51b of the plain portion inner sipe 51 toward the outer side in the tire width direction. It is a range in the tire width direction up to a position in the width direction, and is provided over the entire circumference in the tire circumferential direction in this range. In other words, in the plain portion 70, the inner boundary in the tire width direction is the position in the tire width direction of the outer end 51b of the plain portion inner sipe 51, and the outer boundary in the tire width direction is the shoulder lug groove 46 or the shoulder sipe It is a position in the tire width direction of the inner end portions 46a, 47a of 47. The plane portion inner sipe 51 is formed between the plane portion 70 and the outermost main groove 35 provided as described above, and one end thereof communicates with the outermost main groove 35.

  Further, in the land portion 20 disposed between the main grooves 30, an inter-main groove sipe 60 which is a sipe extending in the tire width direction and in communication with the main grooves 30 is formed. That is, the inter-main groove sipe 60 is formed in the center land portion 21 which is the land portion 20 defined by the center main groove 31 and the outermost main groove 35. The center land portion 21 is disposed on both sides of the center main groove 31 in the tire width direction, but the inter-main groove sipe 60 formed in the center land portion 21 has one end at each of the center land portions 21. It communicates with the center main groove 31 and the other end communicates with the outermost main groove 35.

  A plurality of inter-main-groove sipes 60 formed in the center land portions 21 on both sides of the central main groove 31 are provided, and the plurality of main-inter-groove sipes 60 are arranged side by side in the tire circumferential direction. The inter-groove sipe 60 extends in the tire width direction and is inclined in the tire circumferential direction with respect to the tire width direction. The inclination direction of the inter-main-groove sipe 60 which is inclined in the tire circumferential direction with respect to the tire width direction is the inter-main-groove sipe formed between the center land portion 21 and the shoulder land portion 23 adjacent to each other via the outermost main groove 35 60 and the plain portion inner sipe 51 are in the same direction. That is, the inter-main groove sipe 60 and the plain portion inner sipe 51 extend in the tire width direction and incline in the tire circumferential direction with respect to the tire width direction, and go from the tire equatorial plane CL side toward the tire width direction outward. At the same time, the directions toward the tire circumferential direction are all inclined in the same direction. In the first embodiment, the inter-main-groove sipe 60 and the plain portion inner sipe 51 both move from the front to the rear in the tire rotation direction from the tire equatorial plane CL to the outside in the tire width direction. It is inclined.

  FIG. 4 is an explanatory view of the positional relationship between the inter-main groove sipe 60 and the plane portion inner sipe 51 shown in FIG. The inter-main groove sipe 60 and the plain inner side sipe 51 are formed on the land portions 20 adjacent to each other via the outermost main groove 35 and communicate with the same outermost main groove 35 and the inner inter-side sipe 60 51 and each other are disposed at positions where they extend from each other. In other words, the inter-main groove sipe 60 and the plane portion inner sipe 51, each of which a plurality are formed, are provided in the same number on the center land portion 21 and the shoulder land portion 23, and the spacing in the tire circumferential direction is the inter-main groove sipe 60 and a plain portion inner side sipe 51 are disposed at substantially the same interval, and the inclination angle in the tire circumferential direction with respect to the tire width direction is also substantially the same. As a result, the inter-main-groove sipe 60 communicating with the same outermost main groove 35 and the plane portion inner sipe 51 are disposed in a positional relationship that is an extension of each other. In other words, the inter-main-groove sipe 60 and the plain-portion inner sipe 51 formed in the center land portion 21 and the shoulder land portion 23 adjacent to each other via the outermost main groove 35 penetrate the outermost main groove 35. It is formed by

  Here, the positional relationship in which the sipes are extended lines with each other is that the center line CS in the groove width direction of at least one of the two target sipes communicates with the same main groove 30 When extending toward the sipe side, the distance between the center lines CS of each sipe at the position where the other sipe communicates with the main groove 30 is within the range of 0 mm or more and 4.0 mm or less. Say.

  Furthermore, the inter-main-groove sipes 60 formed in the center land portions 21 adjacent to each other via the center main groove 31 have mutually opposite directions of inclination in the tire circumferential direction with respect to the tire width direction. The inter-groove sipe 60 is disposed in a positional relationship in which the extension lines from the respective inter-groove sipe 60 formed in different center land portions 21 to the tire equatorial plane CL side intersect on the tire equatorial plane CL It is done. For this reason, the inter-main-groove sipe 60 formed in the center land portion 21 and the shoulder land portion 23 and the plane portion inner-side sipe 51 are located on the extension line of the main groove inter-sipe 60 and When the plane portion inner sipe 51 is viewed as a whole, it is formed in a V-shaped shape in which the apex is located on the tire equatorial plane CL. That is, in the first embodiment, the inter-main-groove sipe 60 and the plane portion inner sipe 51 have apexes on the tire equatorial plane CL, and move from the front to the rear in the tire rotation direction in the tire width direction It is formed in a V-shaped shape whose width is large.

  The inter-main groove sipe 60 and the plane portion inner sipe 51 formed in different land portions 20 are arranged with regularity as described above. Furthermore, the shoulder lug grooves 46 and the shoulder sipes 47 formed in the shoulder land portions 23 located on both sides in the tire width direction are also similar to the inter-main groove sipes 60 and the plain inner side sipes 51 from the front in the tire rotation direction The spacing between the shoulder lug grooves 46 and the shoulder sipes 47 in the tire width direction is increased toward the attachment side. Thereby, the shoulder lug grooves 46 and the shoulder sipes 47 are also arranged with regularity close to the inter-main-groove sipes 60 and the plain portion inner sipes 51.

  The inter-main groove sipe 60 and the plain inner side sipe 51 formed in the center land portion 21 and the shoulder land portion 23 each have a groove depth of 2 mm or more and 8 mm or less within a range of 0.1 mm or more and 2 mm or less. It is in the range.

  Further, in the shoulder land portion 23, a recessed portion 80 recessed from the tread surface 10 is formed on the outer side in the tire width direction of the ground contact end T. The recess 80 is provided near the design end E in the tread surface 10, and is formed in a circular dimple shape having a depth of 0.1 mm to 1 mm within a range of 1 mm to 5 mm in diameter. ing. The recess 80 is disposed on the outer side in the tire width direction than the outer end 47b of the shoulder sipe 47, that is, in the tire width direction in the portion between the shoulder lug grooves 46 adjacent in the tire circumferential direction. It arrange | positions in the position in which the sipe 47 is not formed. In the first embodiment, the recesses 80 are arranged in two rows in each of the tire width direction and the tire circumferential direction between the shoulder lug grooves 46 adjacent to each other in the tire circumferential direction, that is, in the tire circumferential direction Four are provided between adjacent shoulder lug grooves 46.

  FIG. 5 is an explanatory view of the widths and positions of the main groove 30 and the plane portion 70 shown in FIG. The plurality of main grooves 30 formed in the tread surface 10 each have a groove width WG within a range of 3% to 10% of the ground contact width TW. In the first embodiment, the three main grooves 30 are The groove width WG is in the range of 3% to 7% of the ground contact width TW. Further, among the three main grooves 30, the outermost main grooves 35 disposed on both sides of the tire equatorial plane CL in the tire width direction are the distance from the tire equatorial plane CL to the groove width center CG of the outermost main groove 35 DG is disposed at a position where it is in the range of 10% or more and 20% or less of the ground contact width TW. The contact width TW in this case is the distance between the contact ends T of the tread surface 10 in the tire width direction.

  On the other hand, at least a portion of the plain portions 70 provided on both sides of the tire equatorial plane CL in the tire width direction is in the range of 22% to 38% of the ground contact width TW in the tire width direction from the tire equatorial plane CL. ing. In the plane portion 70, the plane width WP, which is the width in the tire width direction, is in the range of 8.5% to 15% of the ground contact width TW, and the total of the plurality of plane portions 70 in the tire width direction The width, that is, the total width of the two plane portions 70 is in the range of 17% to 30% of the ground width TW. In the plane portion 70, the distance DP from the tire equatorial plane CL to the plane width center CP in the tire width direction of the plane portion 70 is within a range of 25% to 35% of the ground contact width TW. It is preferred to be located at

  As described above, in the tread surface 10 on which the grooves such as the main groove 30 are formed, the groove area ratio of the main groove 30 is in the range of 15% to 20%, and the grooves excluding the plurality of main grooves 30 are excluded. The groove area ratio of the grooves is in the range of 2% to 8%. Moreover, the groove area ratio which united all the grooves formed in the tread surface 10 is in the range of 17% or more and 28% or less. The groove area ratio here is defined by the percentage of groove area / (groove area + grounding area). The groove area is the sum of the opening areas of the grooves to be calculated in the ground plane (ground area). The groove area and the ground contact area are measured when the pneumatic tire 1 is rim-assembled on a regular rim, and the regular internal pressure is filled and 88% of the regular load is applied.

  When mounting the pneumatic tire 1 according to the first embodiment to a vehicle, the pneumatic tire 1 is mounted on the rim wheel by fitting the rim wheel to the bead portion 5 and the air is filled inside. Wear it on a vehicle in an inflated condition. At that time, since the pneumatic tire 1 according to the first embodiment has a designated rotational direction, the pneumatic tire 1 that rotates when the vehicle advances advances in a direction in which the pneumatic tire 1 rotates in the designated rotational direction. Wear the tire 1 on a vehicle. Specifically, the sipe 60 between the main grooves, the inner side sipe 51, the shoulder lug groove 46, and the shoulder sipe 47, which are formed to be inclined in the tire circumferential direction with respect to the tire width direction, Each vehicle is attached to the vehicle in a direction in which the tire gradually comes in contact with the tire width direction outer side from the tire width direction inner side. Alternatively, the apex side of the V of the main groove between the main groove sipe 60 and the plane inner side sipe 51 disposed in an extended line with each other and disposed in a V shape when viewed as a whole is a tire It is mounted in the direction that is located on the first arrival side in the rotational direction.

  When the vehicle equipped with the pneumatic tire 1 travels, the pneumatic tire 1 rotates while the tread surface 10 of the portion of the tread surface 10 located below contacts the road surface. The vehicle travels by transmitting a driving force or a braking force to the road surface or generating a turning force by the frictional force between the tread surface 10 and the road surface. For example, when traveling on a dry road surface with a vehicle equipped with the pneumatic tire 1, the driving force or the braking force is transmitted to the road surface mainly by the frictional force between the tread surface 10 and the road surface, or the turning force Travel by generating or. In addition, when traveling on a wet road surface, water between the tread surface 10 and the road surface enters grooves such as the main groove 30 and the shoulder lug grooves 46, and these grooves cause the water to flow between the tread surface 10 and the road surface. Run while draining the water. As a result, the tread surface 10 easily contacts the road surface, and the frictional force between the tread surface 10 and the road surface enables the vehicle to travel as desired.

  Here, in the pneumatic tire 1 according to the first embodiment, the rotational direction is specified, and the inter-main-groove sipes 60 formed on the tread surface 10, the plain portion inner sipes 51, the shoulder lug grooves 46, and the shoulder sipes 47. When the pneumatic tire 1 rotates, the tire gradually comes in contact with the tire width direction from the inner side toward the outer side in the tire width direction. As a result, water between the tread surface 10 and the road surface can be drained from the tire equatorial plane CL side toward the tire width direction outer side by these sipes or the like as the pneumatic tire 1 rotates, and drainage performance Can be secured. Therefore, wet steering stability, which is steering stability when traveling on a wet road surface, can be improved. Moreover, since the drainage property is secured by designating the rotation direction of the pneumatic tire 1 and arranging the grooves formed on the tread surface 10 with regularity, drainage is not performed without increasing the groove area ratio. As a result, the rigidity of the land portion 20 can be ensured while ensuring the drainage property. As a result, when the pneumatic tire 1 rolls, excessive deformation of the land portion 20 can be suppressed, and rolling resistance can be reduced.

  Further, on the tread surface 10, a plain portion 70 in which a groove is not formed is provided over the entire circumferential direction of the tire, and the plain portion 70 has a ground width TW in the tire width direction from the tire equatorial plane CL. At least a portion is located within the range of 22% to 38%. As a result, it is possible to stabilize the vibration due to the deformation of deflection during rolling of the pneumatic tire 1, and to suppress the increase in road noise due to the instability of the vibration.

  FIG. 6 is an explanatory view showing the relationship between the tread pattern shown in FIG. 2 and the magnitude of the amplitude in the cross-section second-order natural vibration mode. At the time of rolling of the pneumatic tire 1, the tread portion 2 is rotated while the tread portion 2 is repeatedly bent because the pneumatic tire 1 is rotated while repeating contact and separation of the tread surface 10 on the road surface. As a result, the tread portion 2 vibrates by repeating the amplitude in the form of a so-called steady wave due to the bending of the pneumatic tire 1 when rolling. Since the tread portion 2 vibrates in the form of a steady wave in this manner when the pneumatic tire 1 rolls, the amplitude of the vibration wave V of the tread portion 2 in the cross-section secondary natural vibration mode representing the vibration state of the tread portion 2 The size of V depends on the position in the tire width direction.

  The amplitude of the vibration wave V in the cross-section second-order natural vibration mode is the largest near the tire equatorial plane CL, as shown in FIG. 6, and decreases toward the tire width direction outer side from the tire equatorial plane CL. The distance from the center in the tire width direction in the range between the equatorial plane CL and the ground contact end T increases toward the tire width direction outer side. That is, in the cross-sectional second-order natural vibration mode, the so-called antinode Va of the stationary wave where the amplitude of the vibration wave V becomes largest is located near the tire equatorial plane CL, and in the range between the tire equatorial plane CL and the ground end T A node Vn at which the amplitude of the vibration wave V is the smallest is located near the center in the tire width direction. Further, the nodes Vn of the vibration wave V are located on both sides of the tire equatorial plane CL in the tire width direction, and the two nodes Vn are each 8.5 of the contact width TW in the tire width direction from the tire equatorial plane CL. It is located in the range of% or more and 15% or less.

  At least a portion of the plain portion 70 of the tread surface 10 is located in the range of 22% to 38% of the ground contact width TW in the tire width direction from the tire equatorial plane CL. It is located at the node Vn of the vibration wave V in the natural vibration mode. Thus, the rigidity of the tread portion 2 in the vicinity of a position corresponding to the node Vn of the vibration wave V in the cross-section second-order natural vibration mode is high, and the tread portion 2 is hardly deformed at the position of the node Vn. That is, the plain portion 70 has high rigidity because no groove is formed over the entire circumference of the tire circumferential direction, and the position of the plain portion 70 in the tire width direction is the position of the node Vn in the tire width direction As a result, the deformation of the tread portion 2 at the position of the node Vn can be reduced. Therefore, when the pneumatic tire 1 rolls, it is possible to suppress that the tread portion 2 is easily vibrated at the node Vn of the vibration wave V in the cross-section secondary natural vibration mode, and the frequency of the cross-section secondary natural vibration mode Since the height can be increased, road noise can be reduced.

  Further, in the plain portion 70, the total width of the plurality of plain portions 70 in the tire width direction is in the range of 17% to 30% of the ground contact width TW, so the tread portion 2 vibrates at the node Vn. It can be more reliably suppressed that it becomes easy to do. That is, when the total width of the plane portion 70 is less than 17% of the ground contact width TW, the total width of the plane portion 70 is too narrow, and it may be difficult to secure the rigidity of the tread portion 2 even if the plane portion 70 is provided. There is. In this case, even if the plane portion 70 is provided, it may be difficult to suppress the tendency of the tread portion 2 to easily vibrate at the node Vn of the cross-section secondary natural vibration mode. When the total width of the plane portion 70 exceeds 30% of the ground width TW, the total width of the plane portion 70 is too wide, so the rigidity of the tread portion 2 at a position other than the node Vn of the cross-section secondary natural vibration mode There is a possibility that the plane unit 70 may increase the pressure. In this case, since the difference between the rigidity at the node Vn of the cross-section second-order natural vibration mode in the tread portion 2 and the rigidity at positions other than the node Vn is reduced, the tread portion 2 In addition to the position other than the node Vn, there is a possibility that the vibration easily occurs at the position of the node Vn.

  On the other hand, when the total width of the plurality of plane portions 70 is within the range of 17% to 30% of the ground contact width TW, the rigidity at the position of the node Vn in the tread portion 2 is set to a position other than the node Vn. The rigidity of the node V can be more reliably increased, and the ease of vibration at the node V n can be more reliably suppressed. Thus, the frequency of the cross-sectional second-order natural vibration mode can be more reliably increased, and road noise can be reduced more reliably.

  Furthermore, in the tread surface 10, since the groove area ratio of the grooves excluding the plurality of main grooves 30 is in the range of 2% to 8%, the main groove 30 is secured while drainage of grooves other than the main groove 30 is ensured. The rolling resistance can be reduced by suppressing the deformation of the land portion 20 defined by 30. That is, when the groove area ratio of the grooves excluding the main groove 30 is less than 2%, the groove area ratio is too small, so it is difficult to drain water between the tread surface 10 and the road surface by grooves other than the main groove 30. There is a risk. In addition, when the groove area ratio of the grooves excluding the main groove 30 exceeds 8%, it becomes difficult to secure the rigidity of the land portion 20 defined by the main groove 30, and the land portion 20 is easily deformed. May increase. On the other hand, when the groove area ratio of the grooves excluding the main groove 30 is in the range of 2% to 8%, the deformation of the land portion 20 is suppressed while securing drainage with grooves other than the main groove 30. Rolling resistance can be reduced. As a result of these, it is possible to achieve both suppression of deterioration of rolling resistance and reduction of road noise while improving wet steering.

  In addition, since the plane width WP is in the range of 8.5% to 15% of the ground width TW of the plane portion 70, the tread portion 2 is more reliably suppressed from being easily vibrated at the node Vn. can do. That is, when the plane width WP of the plane portion 70 is less than 8.5% of the ground width TW, the plane width WP is too narrow, and it may be difficult to secure the rigidity of the tread portion 2 even if the plane portion 70 is provided. There is. In this case, even if the plane portion 70 is provided, it may be difficult to suppress the tendency of the tread portion 2 to easily vibrate at the node Vn of the cross-section secondary natural vibration mode. When the plane width WP of the plane portion 70 exceeds 15% of the ground width TW, the plane width WP is too wide, so the rigidity of the tread portion 2 at a position other than the node Vn of the cross-section secondary natural vibration mode is There is a possibility that it may be increased by 70. In this case, since the difference in rigidity between the position of the node Vn of the tread portion 2 and the position other than the node Vn is difficult to obtain, when the pneumatic tire 1 rolls, the tread portion 2 is not only at the position other than the node Vn. Also, there is a possibility that the vibration easily occurs even at the position of the node Vn.

  On the other hand, when the plane width WP of the plane portion 70 is in the range of not less than 8.5% and not more than 15% of the ground contact width TW, the rigidity at the position of the node Vn in the tread portion 2 is a position other than the node Vn. The rigidity of the node V can be more reliably increased, and the ease of vibration at the node V n can be more reliably suppressed. As a result, the frequency of the cross-sectional second-order natural vibration mode can be more reliably increased, and road noise can be reduced more reliably.

  Further, the outermost main groove 35 is disposed at a position where the distance DG from the tire equatorial plane CL to the groove width center CG of the outermost main groove 35 is in the range of 10% to 20% of the ground contact width TW. Therefore, the rigidity of the center land portion 21 and the rigidity of the shoulder land portion 23 can be secured in a well-balanced manner. That is, when the distance DG from the tire equatorial plane CL to the groove width center CG of the outermost main groove 35 is less than 10% of the ground contact width TW, in the tire width direction of the outermost main groove 35 and the center main groove 31 The distance may be too small, and the width of the center land portion 21 in the tire width direction may be too narrow. In this case, the rigidity of the center land portion 21 may be too low, and the dry steering stability, which is the steering stability when traveling on a dry road surface, may be reduced. Further, when the distance DG from the tire equatorial plane CL to the groove width center CG of the outermost main groove 35 exceeds 20% of the ground contact width TW, the outermost main groove 35 is too close to the tire width direction outer side, The width of the land portion 23 in the tire width direction may be too narrow. In this case, the rigidity of the shoulder land portion 23 may be too low, and the dry steering stability may be reduced.

  On the other hand, when the distance DG from the tire equatorial plane CL to the groove width center CG of the outermost main groove 35 is in the range of 10% to 20% of the contact width TW, the center land portion 21 and the shoulder land The width in the tire width direction of any land portion 20 with the portion 23 can be set to an appropriate size, and the rigidity of the center land portion 21 and the rigidity of the shoulder land portion 23 can be secured in a well-balanced manner. As a result, dry handling can be ensured while reducing road noise.

  Further, since the groove width WG of each of the plurality of main grooves 30 is in the range of 3% to 10% of the ground contact width TW, drainage of the main grooves 30 is ensured while securing the rigidity of the land portion 20. be able to. That is, when the groove width WG of the main groove 30 is less than 3% of the ground contact width TW, the groove width WG of the main groove 30 is too narrow, and it becomes difficult to secure drainage in the main groove 30. There is a risk that it will be difficult to improve the quality. When the groove width WG of the main groove 30 exceeds 10% of the ground contact width TW, the groove width WG of the main groove 30 is too wide, so the width of the land portion 20 defined by the main groove 30 in the tire width direction The rigidity of the land portion 20 may be reduced due to the narrowing of the width, and the dry steering stability may be reduced.

  On the other hand, when the groove width WG of the main groove 30 is in the range of 3% to 10% of the ground contact width TW, the groove width WG of the main groove 30 is such that the rigidity of the land portion 20 is not excessively reduced. It is possible to secure the drainage performance in the main groove 30 more reliably while suppressing the decrease in the rigidity of the land portion 20. As a result, it is possible to achieve both dry steering and wet steering.

  Further, three main grooves 30 are provided, and each of three main grooves 30 has a groove width WG of 3% or more and 7% or less of the ground contact width TW. The total can be in the range of 9% to 21% of the ground contact width TW. Thereby, the drainage property in the main groove 30 can be secured while securing the rigidity of the land portion 20 more reliably. That is, when the total of the groove widths WG of the three main grooves 30 is less than 9% of the ground contact width TW, the total of the groove widths WG is too small, and the drainage in the main grooves 30 is appropriately secured. May become difficult, and it may be difficult to secure wet handling. In addition, when the total of the groove widths WG of the three main grooves 30 exceeds 21% of the ground contact width TW, the total of the groove widths WG is too large, so it is difficult to appropriately secure the rigidity of the land portion 20 As a result, there is a risk that it will be difficult to ensure dry handling.

  On the other hand, when the groove width WG of each of the three main grooves 30 is in the range of 3% to 7% of the ground width TW, the total of the groove widths WG of the main grooves 30 is the ground width TW. The sum of the groove widths WG of the three main grooves 30 can be set to an appropriate size when it is within the range of 9% or more and 21% or less of, and the decrease in the rigidity of the land portion 20 is more reliably suppressed. At the same time, drainage in the main groove 30 can be secured. As a result, it is possible to more reliably achieve both dry and wet operations.

  In addition, since a plain inner side sipe 51 extending in the tire width direction and having the inner end 51a communicating with the outermost main groove 35 is formed between the plain portion 70 and the outermost main groove 35, the shoulder land portion The rigidity of the portion in the vicinity of the outermost main groove 35 can be reduced. Thus, the contact pressure in the vicinity of the outermost main groove 35 in the shoulder land portion 23 can be prevented from becoming too high, and the contact pressure of the tread surface 10 can be made uniform. As a result, the deterioration of the rolling resistance can be suppressed more reliably.

  Further, in the center land portion 21 disposed between the center main grooves 31, there is formed a sipe 60 between the main grooves which extends in the tire width direction and one end thereof communicates with the center main groove 31. The rigidity of the portion in the vicinity of the center main groove 31 can be reduced. Thereby, it can suppress that the contact pressure in the center main groove 31 vicinity in the center land part 21 becomes high too much, and equalization | homogenization of the contact pressure of the tread surface 10 can be achieved. As a result, the deterioration of the rolling resistance can be suppressed more reliably.

  In addition, the plain portion inner sipe 51 and the inter-main-groove sipe 60 are formed in the land portions 20 adjacent to each other via the outermost main groove 35, and the sipes 51, 60 communicating with the same outermost main groove 35 are mutually Since the lands 20 are disposed at the positions of the extension lines, the rigidity can be equalized in the land portions 20 adjacent to each other through the outermost main groove 35. Thereby, equalization of the contact pressure of tread surface 10 can be attained more certainly. Further, when going from the tire equatorial plane CL side to the tire width direction outer side, the plain portion inner side sipe 51 and the inter-main groove sipe 60 inclined in the tire circumferential direction with respect to the tire width direction are respectively All the slopes in the same direction are arranged on the extension line, so the water between the tread surface 10 and the road surface is more reliable between the main groove sipe 60 and the plane portion inner sipe 51 It is possible to drain water from the tire equatorial plane CL side to the outside in the tire width direction. As a result of these, it is possible to suppress the deterioration of the rolling resistance while improving the wet steering stability more reliably.

  Further, the shoulder groove portion 40 formed in the shoulder land portion 23 is disposed between the plurality of shoulder lug grooves 46 extending in the tire width direction and the shoulder lug grooves 46 adjacent in the tire circumferential direction in the tire width direction. By having the shoulder sipe 47 extended, the rigidity of the shoulder land portion 23 can be made uniform in the tire circumferential direction. As a result, the contact pressure can be prevented from becoming nonuniform due to the rigidity of the shoulder land portion 23 partially increasing, and the contact pressure on the tread surface 10 can be more reliably made uniform. Can. As a result, the deterioration of the rolling resistance can be more reliably suppressed.

  Moreover, since the recessed part 80 is formed in the tire width direction outer side of the earthing | grounding end T in the shoulder land part 23, a turbulent flow is generated to air by the recessed part 80 at the time of rolling of the pneumatic tire 1, and the air from the tire surface Peeling can be suppressed. Thereby, air resistance can be reduced, and as a result, deterioration of rolling resistance can be more reliably suppressed.

  Further, since the groove area ratio of the main groove 30 of the tread surface 10 is in the range of 15% to 20%, the drainage property of the main groove 30 is ensured while securing the rigidity of the land portion 20 more reliably. can do. That is, when the groove area ratio of the main groove 30 is less than 15%, the groove area ratio of the main groove 30 is too small, and it becomes difficult to appropriately ensure the drainage property in the main groove 30, There is a risk that it will be difficult to secure the safety. In addition, when the groove area ratio of the main groove 30 exceeds 20%, the groove area ratio of the main groove 30 is too large, so it becomes difficult to appropriately secure the rigidity of the land portion 20, resulting in dry steering stability. There is a risk that it will be difficult to secure.

  On the other hand, when the groove area ratio of the main groove 30 is in the range of 15% or more and 20% or less, the drainage property in the main groove 30 is secured while suppressing the decrease in the rigidity of the land portion 20 more reliably. Can. As a result, it is possible to more reliably achieve both dry and wet operations.

Second Embodiment
The pneumatic tire 1 according to the second embodiment has substantially the same configuration as the pneumatic tire 1 according to the first embodiment, but is characterized in that there are two main grooves 30. The other configuration is the same as that of the first embodiment, and thus the description thereof is omitted and the same reference numeral is attached.

  FIG. 7 is a plan view of the tread portion 2 of the pneumatic tire 1 according to the second embodiment. The pneumatic tire 1 according to the second embodiment has the rotation direction specified in the same manner as the pneumatic tire 1 according to the first embodiment, and rotates in the designated rotation direction about the rotation axis when the vehicle advances. The pneumatic tire 1 is mounted on the vehicle. Further, in the pneumatic tire 1 according to the second embodiment, in the same manner as the pneumatic tire 1 according to the first embodiment, the shoulder land portion 23 is formed with the shoulder groove portion 40 which is separated from the outermost main groove 35. Plain portions 70 are respectively disposed between the outermost main grooves 35 and the shoulder groove portions 40 on both sides of the tire equatorial plane CL. Also in the second embodiment, at least a portion of the plane portion 70 is located in the range of 22% to 38% of the ground contact width TW in the tire width direction from the tire equatorial plane CL.

  Also, as the shoulder groove portion 40, the shoulder lug grooves 46 and the shoulder sipes 47 are provided as in the first embodiment, and both the shoulder lug grooves 46 and the shoulder sipes 47 go from the inside to the outside in the tire width direction. In the tire rotational direction, the tire is inclined in the direction from the first attachment side to the second attachment side. Further, in the shoulder land portion 23, a dimple-shaped concave portion 80 is formed in the vicinity of the design end E on the outer side in the tire width direction of the ground contact end T.

  The second embodiment differs from the first embodiment in the number of main grooves 30, and the pneumatic tire 1 according to the second embodiment has two main grooves 30 formed on the tread surface 10. For this reason, the two main grooves 30 are all the outermost main grooves 35 located at both ends in the tire width direction. Further, in the two main grooves 30 formed in the tread surface 10, the groove width WG is in the range of 5% to 10% of the ground contact width TW.

  Further, with the number of main grooves 30 being two, the land portion 20 defined by the main grooves 30 is disposed between the two outermost main grooves 35 and disposed on the tire equatorial plane CL. A center land portion 21 which is a land portion 20 and a shoulder land portion 23 which is a land portion 20 located on the outer side of the outermost main groove 35 in the tire width direction are provided.

  Between the plain portion 70 and the outermost main groove 35 in the shoulder land portion 23, a plain portion inner sipe 51 extending in the tire width direction and in which the inner end 51a communicates with the outermost main groove 35 is formed. The plane portion inner side sipe 51 in the second embodiment is inclined in the direction from the first attachment side to the rear attachment side in the tire rotation direction as it goes from the inner side to the outer side in the tire width direction, as in the first embodiment. The plain portion 70 disposed in the shoulder land portion 23 is the inner side of the shoulder lug groove 46 and the shoulder sipe 47 from the position in the tire width direction of the outer end 51 b of the plain portion inner sipe 51 toward the tire width direction. It is a range in the tire width direction up to the position in the tire width direction of the end portions 46a, 47a, and is provided over the entire circumference in the tire circumferential direction in this range.

  Further, in the center land portion 21 disposed between the main grooves 30, an inter-main groove sipe 60 which is a sipe extending in the tire width direction and in communication with the main grooves 30 is formed. Both ends of the sipe 60 between the main grooves in the second embodiment communicate with the outermost main grooves 35 different from each other, and the tire rotation is performed from the center in the tire width direction of the center land portion 21 toward the tire width direction outer side. It inclines in the direction from the first arrival side to the second side in the direction. That is, the inter-main-groove sipe 60 has a bent portion 65 in the vicinity of the center in the tire width direction of the center land portion 21 where the angle of inclination with respect to the tire width direction changes. As it goes to the outside, it is inclined in the direction from the first attachment side to the rear attachment side in the tire rotation direction. For this reason, in the inter-main-groove sipe 60, the position of the bending portion 65 is located closest to the front end in the tire rotation direction. In the second embodiment, the bending portion 65 of the inter-main groove sipe 60 is located on the tire equatorial plane CL.

  Further, since the inter-main-groove sipe 60 has the bending portion 65 in this manner, the portion on the side of the outermost main groove 35 from the bending portion 65 in the inter-main-groove sipe 60 and the outermost main groove The plain portion inner side sipe 51 communicating with 35 is inclined in the same direction with respect to the tire width direction. That is, the inter-main groove sipe 60 and the plain portion inner sipe 51 extend in the tire width direction and are inclined in the tire circumferential direction with respect to the tire width direction, and go from the tire equatorial plane CL side toward the tire width direction outward. At the same time, the directions toward the tire circumferential direction are all inclined in the same direction.

  Furthermore, an inter-main-groove sipe 60 and a plane portion inner-side sipe 51 formed in the center land portion 21 and the shoulder land portion 23 adjacent to each other via the same outermost main groove 35 communicate with the same outermost main groove 35, They are arranged at positions extending along each other. For this reason, when the inter-main-groove sipe 60 and the plane portion inner sipe 51 are located on an extended line with each other, the inter-main-groove sipe 60 and the plane portion inner sipe 51 are viewed as a whole. The bent portion 65 of the inter-main groove sipe 60 is formed in a V-shaped shape located on the tire equatorial plane CL.

  In other words, the inter-main-groove sipe 60 and the plain inner side sipe 51 are positioned on the tire equatorial plane CL with the bent portion 65 of the inter-main-groove sipe 60 at the apex of the V shape. It is formed in a V-shaped shape in which the width in the tire width direction becomes larger as it goes to the wearing side. As described above, the inter-main-groove sipe 60 and the plain-portion inner sipe 51 formed in the center land portion 21 and the shoulder land portion 23 adjacent to each other through the outermost main groove 35 penetrate the outermost main groove 35. And the inter-groove sipe 60 and the plane portion inner sipe 51 together form a V-shaped relationship.

  Further, as in the first embodiment, the groove area ratio of the main groove 30 is in the range of 15% or more and 20% or less, and the groove area ratio of the groove excluding the main groove 30 is the groove area ratio of the tread surface 10 Is in the range of 2% to 8%.

  In the second embodiment, even if the number of main grooves 30 is two, the plain portions 70 are provided on both sides of the tire equatorial plane CL in the tire width direction, so the node Vn of the vibration wave V in the cross-section second-order natural vibration mode Deformation of the tread portion 2 at the position can be reduced. As a result, when the pneumatic tire 1 rolls, it is possible to suppress that the tread portion 2 is easily vibrated at the node Vn of the vibration wave V in the cross-section second-order natural vibration mode, and the frequency of the second-section second-order natural vibration mode Since the height can be increased, road noise can be reduced. In addition, since the groove area ratio of the grooves excluding the main groove 30 is in the range of 2% to 8%, the land portion defined by the main groove 30 while securing the drainage property with the grooves other than the main groove 30. The rolling resistance can be reduced by suppressing the deformation of 20.

  In the second embodiment, the rotational direction is also specified, and the inter-main groove sipe 60, the plain inner side sipe 51, the shoulder lug grooves 46, and the shoulder sipe 47 each rotate from the inner side in the tire width direction when the pneumatic tire 1 rotates. In order to ground gradually toward the tire width direction outer side, water between the tread surface 10 and the road surface can be drained from the tire equatorial plane CL side toward the tire width direction outer side. As a result of these, it is possible to achieve both suppression of deterioration of rolling resistance and reduction of road noise while improving wet steering.

  Further, since the two main grooves 30 each have a groove width WG within a range of 5% to 10% of the ground contact width TW, the total of the groove widths WG of the main grooves 30 is 10% or more of the ground contact TW It can be in the range of 20% or less. As a result, the sum of the groove widths WG of the two main grooves 30 can be set to an appropriate size, and the drainage of the main grooves 30 can be ensured while ensuring the rigidity of the land portion 20 more reliably. Can. As a result, it is possible to more reliably achieve both dry and wet operations.

[Modification]
In the first and second embodiments described above, the plain portions 70 are provided at two locations on both sides of the tire equatorial plane CL in the tire width direction, but the plain portions 70 may be other than two locations. The plane portion 70 is provided on both sides of the tire equatorial plane CL in the tire width direction, and at least a portion is positioned within a range of 22% to 38% of the ground contact width TW in the tire width direction from the tire equatorial plane CL. If it does, the number does not matter. Further, the distance in the tire width direction from the tire equatorial plane CL and the plane width WP may be different among the plurality of plane portions 70. Similarly, the groove widths WG of the plurality of main grooves 30 may be different from each other, and the distances DG from the tire equatorial plane CL to the groove width center CG of the outermost main grooves 35 are different between the outermost main grooves 35. It may be

  In the first and second embodiments described above, the shoulder lug grooves 46 and the shoulder sipes 47 provided as the shoulder groove portions 40 are alternately disposed in the tire circumferential direction, but the shoulder lug grooves 46 and the shoulder sipes 47 Are not necessarily arranged alternately. In the first and second embodiments, the position of the inner end 46a of the shoulder lug groove 46 in the tire width direction and the position of the inner end 47a of the shoulder sipe 47 in the tire width direction are substantially the same. The positions in the tire width direction may be different from each other.

  In the first and second embodiments described above, the shoulder lug groove 46 and the shoulder sipe 47 are provided as the shoulder groove portion 40. However, the shoulder groove portion 40 is either the shoulder lug groove 46 or the shoulder sipe 47. May be Further, the shoulder groove portion 40 may be provided with a groove other than the shoulder lug groove 46 and the shoulder sipe 47 as the shoulder groove portion 40. For example, a narrow groove formed in the shoulder land portion 23 and extending in the tire circumferential direction 40 may be provided. In this case, the position in the tire width direction of the inner edge of the narrow groove extending in the tire circumferential direction in this way is the end of the plain portion 70 on the outer side in the tire width direction.

  Further, in the first and second embodiments described above, the plain portion inner groove portion 50 is provided by the plain portion inner sipe 51 extending in the tire width direction, but the grooves other than the plain portion inner sipe 51 serve as the plain portion inner groove portion 50. It may be provided. The plain portion inner groove portion 50 extends, for example, in the tire width direction between the plain portion 70 and the outermost main groove 35, and a lug groove in which the inner end in the tire width direction communicates with the outermost main groove 35 It may be provided as the side groove portion 50. Alternatively, both the lug groove and the plain portion inner sipe 51 may be provided as the plain portion inner groove portion 50.

[Example]
8A to 8C are charts showing the results of performance tests of pneumatic tires. Hereinafter, the performance of the pneumatic tire 1 described above is performed for the pneumatic tire of the conventional example, the pneumatic tire 1 according to the present invention, and the pneumatic tire of the comparative example to be compared with the pneumatic tire 1 according to the present invention The evaluation test of The performance evaluation test includes road noise and rolling resistance when the pneumatic tire 1 rolls, dry steering stability which is steering stability on a dry road surface, and wet steering safety which is steering stability on a wet road surface. The test about sex was done.

  The performance evaluation test was conducted by adjusting a pneumatic tire 1 of 195 / 65R15 size called JATMA-designated tire to a JATMA standard rim wheel with a rim size of 15 × 6 J and adjusting the air pressure to 250 kPa. Also, in the tests on road noise, dry steering stability and wet steering stability, the test tire was mounted on a front wheel drive test vehicle with a displacement of 1.8 L and tested by a single passenger ride. .

  The evaluation method of each test item is road noise, by the test vehicle equipped with the test tire, the road noise level when traveling at a speed of 60 km / h on the road course of the test course, by sensory evaluation of the test driver Compared. The road noise is evaluated by representing the sensory evaluation of the test driver as an index with a conventional example described later as 100, and the larger the index, the smaller the road noise and the better the road noise performance.

  Moreover, about rolling resistance, the indoor drum test machine (drum diameter: 1707 mm) was used, and the rolling resistance coefficient in the conditions of load 4.8kN and speed 80 km / hour was computed based on ISO28580. The result is indicated by an index where the reciprocal of the rolling resistance coefficient in the conventional example described later is 100. The larger the index, the lower the rolling resistance.

  In addition, with regard to dry steering safety, a test vehicle equipped with a test tire performs sensory evaluation by a test driver when traveling on a test road on a dry road surface, and the sensory evaluation is an index using a conventional example described later as 100. It evaluated by expressing. The larger the value is, the better the dry maneuverability is.

  In addition, with regard to wet steering safety, a test vehicle equipped with a test tire performs sensory evaluation by a test driver when traveling on a test course on a wet road surface, and the sensory evaluation is an index based on a conventional example described later as 100. It evaluated by expressing. The larger the value is, the better the wet maneuverability is.

  The performance evaluation test compares the pneumatic tire according to the conventional example, which is an example of the conventional pneumatic tire, with the first to eighteenth embodiments which are the pneumatic tire 1 according to the present invention, and the pneumatic tire 1 according to the present invention. It carried out about 23 types of pneumatic tires with comparative examples 1-4 which are pneumatic tires. Among these, in the pneumatic tire of the conventional example, the total width of the plane widths WP of the plurality of plane portions 70 is not within the range of 17% or more and 30% or less of the ground contact width TW. In the pneumatic tires of Comparative Examples 1 to 4, the total width of the plane widths WP of the plurality of plane portions 70 is within the range of 17% to 30% of the ground width TW. The groove area ratio is not within the range of 2% to 8%, or the plain portion 70 is positioned within the range of 8.5% to 15% of the ground contact width TW in the tire width direction from the tire equatorial plane CL. Or the rotational direction of the pneumatic tire is not specified.

  On the other hand, in Examples 1 to 18 which are an example of the pneumatic tire 1 according to the present invention, the total width of the plane widths WP of all the plurality of plane portions 70 is within the range of 17% to 30% of the ground width TW. The groove area ratio of the grooves excluding the main groove 30 is in the range of 2% to 8%, and at least a part of the plain portion 70 is a ground contact width TW in the tire width direction from the tire equatorial plane CL. It is located in the range of 22% or more and 38% or less, and the rotation direction is designated. Further, in the pneumatic tire 1 according to Examples 1 to 18, the number of main grooves 30, the plane width WP of the plane portion 70 with respect to the ground contact width TW, and the groove width WG of the main groove 30 with respect to the ground contact width TW A distance DG [%] from the tire equatorial plane CL to the groove width center CG of the outermost main groove 35 with respect to the ground contact width TW, presence or absence of the plain inner groove portion 50, presence or absence of the inter-main groove sipe 60, shoulder lug grooves 46 Whether or not the sipes of the plurality of land portions 20 are formed in a V-shape as a whole, with the presence or absence of the shoulder sipes 47 between the sipes 47 communicating with the same main groove 30 being disposed on the extension line; The presence or absence of the recess 80 on the tire width direction outer side of the ground contact end T and the groove area ratio [%] of the main groove 30 are different from each other.

  As a result of conducting a performance evaluation test using these pneumatic tires 1, as shown to FIG. 8A-FIG. 8C, the pneumatic tire 1 which concerns on Examples 1-18 compares with a prior art example and Comparative Examples 1-4, and a comparison. It has been found that the wet handling can be improved while suppressing the increase in rolling resistance, and furthermore, the road noise can be reduced. That is, the pneumatic tire 1 according to Examples 1 to 18 can achieve both the suppression of the deterioration of the rolling resistance and the reduction of the road noise while improving the wet handling.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 tread part 3 shoulder part 4 sidewall 5 bead part 6 carcass layer 7 belt layer 10 tread surface 20 land part 21 center land part 23 shoulder land part 30 main groove 31 center main groove 35 outermost main groove 40 Shoulder groove 46 Shoulder lug groove 46a, 47a, 51a Inner end 46b, 47b, 51b Outer end 47 Shoulder sipe 50 Plain portion inner groove 51 Plain portion inner sipe 60 Major groove sipe 65 Bend 70 Plain portion 80

Claims (11)

A pneumatic tire mounted on a vehicle so as to rotate in a designated rotation direction about a rotation axis when the vehicle advances.
A plurality of main grooves formed on the tread surface and extending in the tire circumferential direction;
A plurality of land portions defined by the main groove,
A shoulder land which is the land portion located at the tire width direction outer side of the outermost main groove disposed at both ends in the tire width direction among the plurality of main grooves and disposed at the tire width direction inner side of the ground contact end Department,
A shoulder groove portion formed on the shoulder land portion and separated from the outermost main groove;
A plain portion which is an area which is disposed between the outermost main groove on both sides of the tire width direction center line in the tire width direction and the shoulder groove portion and in which no groove is formed over the entire circumferential direction of the tire. When,
Equipped with
At least a portion of the plain portion is located within a range of 22% to 38% of the contact width in the tire width direction from the tire width direction center line.
In the plane portion, the total width of the plurality of plane portions in the tire width direction is in the range of 17% to 30% of the contact width,
The pneumatic tire is characterized in that a groove area ratio of grooves excluding the plurality of main grooves is in a range of 2% or more and 8% or less of the tread surface.   The pneumatic tire according to claim 1, wherein a width of the plain portion in a tire width direction is in a range of 8.5% to 15% of the contact width. The outermost main groove is disposed at a position where the distance from the tire width direction center line to the groove width center of the outermost main groove is in the range of 10% to 20% of the contact width,
The pneumatic tire according to claim 1 or 2, wherein a groove width of each of the plurality of main grooves is in a range of 3% to 10% of the contact width. There are two main grooves formed in the tread surface,
The pneumatic tire according to claim 3, wherein a groove width of each of the two main grooves is in a range of 5% to 10% of the contact width. There are three main grooves formed in the tread surface,
The pneumatic tire according to claim 3, wherein each of the three main grooves has a groove width within the range of 3% to 7% of the contact width. Between the plain portion and the outermost main groove, there is formed a plain portion inner groove portion which extends in the tire width direction and whose inner end in the tire width direction communicates with the outermost main groove,
The pneumatic tire according to any one of claims 1 to 5, wherein the plain portion is provided on the outer side in the tire width direction from the position in the tire width direction of the outer end of the plain portion inner groove portion in the tire width direction.   The pneumatic tire according to any one of claims 1 to 6, wherein a sipe extending in the tire width direction and communicated with the main groove is formed in the land portion disposed between the main grooves. . Between the plain portion and the main groove, and between the main grooves, there is formed a sipe extending in the tire width direction and at least one end in the tire width direction communicating with the main groove.
A plurality of sipes are disposed in the tire circumferential direction,
The plurality of sipes extend in the tire width direction and incline in the tire circumferential direction with respect to the tire width direction, and when going from the tire width direction centerline side to the tire width direction outer side, the direction in the tire circumferential direction is All are inclined in the same direction,
A plurality of the sipe are disposed at positions where the sipes formed in the land portions adjacent to each other via the outermost main groove communicate with the same outermost main groove are extended lines with each other The pneumatic tire according to any one of claims 1 to 5. The shoulder groove portion is
A plurality of shoulder lug grooves extending in the tire width direction,
A shoulder sipe disposed between the shoulder lug grooves adjacent in the tire circumferential direction and extending in the tire width direction;
The pneumatic tire according to any one of claims 1 to 8, comprising:   The pneumatic tire according to any one of claims 1 to 9, wherein a recess is formed on the outer side in the tire width direction of the ground contact end in the shoulder land portion.   The pneumatic tire according to any one of claims 1 to 10, wherein a groove area ratio of the main groove of the tread surface is in a range of 15% to 20%.

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